At present, a conical reflector is adopted to project a laser beam to form a circular laser plane and thus to form a 360 degrees laser line when projected into space. Compared with the common mode of using four linear laser sources to form a 360 degrees laser line, this projection mode has advantages of lower cost, less energy consumption, compacter structure and better uniformity of laser line. Therefore, this projection mode has superiority in the application on a laser projection apparatus. However, when the conical reflector is applied to the 360 degrees laser projection apparatus, the support problem for the conical reflector has not been well resolved so far. At present, it is common to adopt a photoplastic square-tapered shell or a transparent cylinder to support the conical reflector. Since the cambered surface of the four corners of the square taper or the cylinder would create a secondary projection to the laser line, once the line of the secondary projection is not perpendicular to the laser plane reflected by the conical reflector, the line of the secondary projection of the square taper or the cylinder used for supporting is not overlapped with the 360 degrees laser line reflected by the conical reflector, thus a double-image phenomenon is caused. It is very difficult to adjust the perpendicularity of the square-tapered body or cylinder which is used for supporting. Besides, the photoplastic material is greatly impacted by temperature of the environment and the shape is easy to be changed, causing great influence to the linearity of the laser line and stability and reliability of the use of the apparatus are impacted.